FE Power Forums > FE Technical Forum
2.5" vs 3" Exhaust and Muffler Options
CV355:
Our Mach 1 is going for startup next week, but has to hit the exhaust shop first. I'm debating between 2.5" and 3". I am also looking at Borla ProXS or XR1s for a more unique sound. Pipes will be rear-exit. I have a set of 2.5 Magnaflows and they just weren't all that awe-inspiring. I've put 800hp through 2x 2.5 before, so this is less about performance and more about sound. We're guessing the Mach 1 will be around 700-750hp max when all is said and done, street use only. A few exhaust guys have said you can get 3" under a '69 Mustang but it is tight at the rear axle.
Has anyone run dual 3" on an FE? Was it obnoxiously loud? My wife runs Borla ATAKs (5.0 Coyote), and I ran ATAKs on a '14 GT500, so that's about where I would like to be noise-level for the street. We're not obnoxious drivers either.
Looking for feedback before we start welding things up
cjshaker:
I have the Borla ProXS on my Mach 1. Yes you can get a 3" exhaust on them, but it is tight. It's really tight if you have staggered shocks with the 4spd factory setup. It takes some very careful routing to get them through with the staggered shocks!
Here's a short idle video of my car with the ProXS and 2 1/2" exhaust. I'm a big fan of the ProXS. I think they have a great sound, aren't obnoxiously loud, don't drone at speed and they flow better than most all others I've seen in tests.
https://www.youtube.com/watch?v=PDiG2OSZ0bw
Here's a short in car video to give you an idea of what they sound like at normal acceleration and when you get on it. They will let you know when the loud pedal is smashed, but they still aren't obnoxious or ear splitting. At cruise, which doesn't come through real well on the video, they do have a really nice mellow tone, but they are louder than some people would like. In other words, you can't whisper to the person beside you..lol
https://youtu.be/KhXVsk_Tos4?t=32
I use them on both my Mach 1 and my '70 F350. The Mach has a 497 hp 427. I love them.
fe468stroker:
I have the 3" Magna Flow from the headers out the rear valence cutouts. This is a '68 without the staggered shocks. It is very tight but doable for an experienced exhaust shop. To me the Magna Flow 3" ovals are too loud but are non restrictive. Like you said it is a matter of what sound you like.
CV355:
--- Quote from: fe468stroker on September 22, 2021, 11:34:58 AM ---I have the 3" Magna Flow from the headers out the rear valence cutouts. This is a '68 without the staggered shocks. It is very tight but doable for an experienced exhaust shop. To me the Magna Flow 3" ovals are too loud but are non restrictive. Like you said it is a matter of what sound you like.
--- End quote ---
Loudness is definitely subjective. "Too loud" was when I had a supercharged mod motor, cammed, with headers, catless X pipe and SLP Loudmouths. It was ear-splittingly loud and after two months I had to pull the SLPs and put on a Roush/Magnaflow side exhaust system. I really liked that combo on a mod motor.
We did insulate the Mach 1 with SecondSkin Damplifier Pro and LuxuryLiner MLV. It sounds like a recording studio in the car now. Hopefully that makes a nice loud exhaust a bit more tolerable in the cabin.
--- Quote from: cjshaker on September 22, 2021, 09:52:20 AM ---I have the Borla ProXS on my Mach 1. Yes you can get a 3" exhaust on them, but it is tight. It's really tight if you have staggered shocks with the 4spd factory setup. It takes some very careful routing to get them through with the staggered shocks!
Here's a short idle video of my car with the ProXS and 2 1/2" exhaust. I'm a big fan of the ProXS. I think they have a great sound, aren't obnoxiously loud, don't drone at speed and they flow better than most all others I've seen in tests.
https://www.youtube.com/watch?v=PDiG2OSZ0bw
Here's a short in car video to give you an idea of what they sound like at normal acceleration and when you get on it. They will let you know when the loud pedal is smashed, but they still aren't obnoxious or ear splitting. At cruise, which doesn't come through real well on the video, they do have a really nice mellow tone, but they are louder than some people would like. In other words, you can't whisper to the person beside you..lol
https://youtu.be/KhXVsk_Tos4?t=32
I use them on both my Mach 1 and my '70 F350. The Mach has a 497 hp 427. I love them.
--- End quote ---
That sounds awesome. Decision made :)
cammerfe:
I built an FE for my '63 Effie ICB. Started with a '64 PI engine and did the usual things. Used a set of '64 iron 427 exhaust manifolds and had a complete exhaust system built from three inch 321. Used an X-pipe and had Bassani make me a pair of mufflers with a three foot body. Nipples added to the length. Going up and over the axle was a bit tight. Enough that after several weeks of driving the truck I could just see where the underside of the up-and-over had had slight contact with the axle tubes on each side. The mark was enough to feel and see but I doubt that the pipes were indented by as much as an eighth of an inch.
The sound was very mellow. Had a bit of authority to it. :)
KS
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